This application is based on patent application No. 11-62265 filed in Japan, the contents of which are hereby incorporated by references.
1. Field of the Invention
The present invention relates to a process for the purification of (meth)acrylic acid and/or its ester. Specifically, the present invention relates to a process for the purification of (meth)acrylic acid and/or its ester using a distillation unit comprising a distillation column, a multitubular reboiler, and a pipe connecting the distillation column with the reboiler, which process is capable of preventing the formation of polymerization products in the reboiler and is capable of stably purifying (meth)acrylic acid and/or its ester over a long time.
2. Description of the Related Art
In commercial purification of (meth)acrylic acid and/or its ester, a liquid mixture containing (meth)acrylic acid and/or its ester is generally distilled to separate higher boiling components and lower boiling components contained in the liquid mixture by using a distillation unit including a distillation column, a multitubular reboiler, and a pipe connecting these elements.
Such (meth)acrylic acid and its esters are easily polymerized during the purification process, and it is difficult to prevent polymerization of these compounds in a distillation column for a long time. To this end, Japanese Examined Patent Publications No. 52-34606 and No. 57-61015 each disclose the introduction of a gaseous oxygen from the bottom of a distillation column.
According to the processes disclosed in the above publications, however, although the formation of polymerization product in the distillation column can be avoided, polymerization products form inside the connecting pipe and especially inside tubes constituting the multitubular reboiler which cause clogging of tubes to block the distillation from continuing the purification process.
Accordingly, an object of the invention is to provide a process for the purification of (meth)acrylic acid and/or its ester using a distillation unit comprising a distillation column, a multitubular reboiler, and a pipe connecting these elements, which process is capable of effectively preventing the formation of polymerization products in the reboiler and is capable of stably purifying (meth)acrylic acid and/or its ester over a long time.
After intensive investigations, the present inventors found a process which is capable of preventing the formation of polymerization products in the reboiler and is capable of stably purifying (meth)acrylic acid and/or its ester over a long time.
Such a process is a process for the purification of (meth)acrylic acid and/or its ester using a distillation unit, said distillation unit comprising a distillation column, a multitubular reboiler, and a pipe connecting the distillation column with the multitubular reboiler,
wherein an oxygen containing gas is supplied from at least one point in regions between the distillation column and an inlet of the reboiler and/or in regions between the inlet and an inlet side tube sheet of the multitubular reboiler.